Application of Epithelial Cell Culture in Drug Transport in the Respiratory Tract

Drugs can be inhaled and absorbed throughout the conducting airway from the trachea down to the bronchioles and ultimately in the distal lung across the alveolar epithelium. The respiratory tract offers a large surface area, extensive vasculature, and significantly lower enzymatic activity to favor both local and systemic drug delivery. The respiratory tract is not only structurally but also functionally complex. This must be taken into account in selecting models to learn about the mechanisms as well as factors influencing drug deposition and absorption in the lung. These models fall in five categories: (i) in vivo animal lungs (1 -3 ); (ii) in situ perfused lungs (4 -6 ); (iii) in vitro isolated and perfused lungs or discs punched from strips of trachea (7 -9 ); (iv) in vitro isolated respiratory tract epithelial cells (7 ,10 ); and (v) in vitro cultured epithelial cell monolayers (11 -15 ).